What Mini codes (P0304, P0128, P0011, P0016, P0420, P0171) actually mean on Mini engines — the real cause, the common misdiagnosis, and the honest UK repair cost.
These are the OBD fault codes we see most often on Mini vehicles in the workshop, with the real cause on Mini engines rather than the generic textbook definition, plus the honest independent-garage cost.
Mini fault codes explained
- P0304 — Cylinder 4 misfire on Mini — N14/N18 Prince engine coil/plug failure plus timing chain stretch causing cyl 4 misfire on high-mileage Cooper S. Typical UK cost £140–£1800.
- P0128 — Coolant below thermostat on Mini — the electric thermostat housing on N14/N18 Prince engines is a known failure. Typical UK cost £180–£420.
- P0011 — Intake camshaft over-advanced on Mini Cooper S — the Prince N14/N18 VANOS solenoid and stretched timing chain are the usual suspects. Typical UK cost £220–£1800.
- P0016 — Crank/cam correlation on Mini Cooper S — Prince N14/N18 timing chain stretch is one of the best-known faults in the trade. Typical UK cost £900–£1900.
- P0420 — Catalyst efficiency below threshold on Mini Cooper / Cooper S — typically a knackered cat after years of oil-burning Prince engines. Typical UK cost £250–£1400.
- P0171 — System too lean on Mini — Prince N14/N18 PCV diaphragm and intake gaskets are the classic causes. Typical UK cost £240–£650.
- P0017 — Crank to exhaust cam correlation on Mini — Prince timing chain has stretched, partner code to P0016. Typical UK cost £900–£1900.
- P0014 — Exhaust cam over-advanced on Mini Cooper S — Prince VANOS solenoid sludging or chain stretch. Typical UK cost £180–£1900.
- P0299 — Turbo underboost on Mini Cooper S — PCV diaphragm leak and charge pipe splits are the typical causes. Typical UK cost £180–£1400.
- P0507 — Idle speed higher than expected on Mini — N12/N14/N18 Prince engine vacuum leak from PCV. Typical UK cost £180–£580.
- P0341 — Camshaft position sensor performance on Mini — N12/N14/N18 Prince sensor and VVT solenoid overlap. Typical UK cost £100–£420.
Codes are generic across manufacturers, but the fix is not. The same code on a Mini usually points at a different component than it would on another make, which is why a make-specific diagnosis saves money before any parts are bought.
Reading codes properly on a Mini
A £20 reader pulls generic engine codes and nothing else. On a Mini the useful information often sits in the gearbox, ABS, body or comfort modules, and those need a tool that talks the manufacturer protocols. Just as important is the freeze-frame data stored with the code: engine speed, load, coolant temperature and fuel trims at the exact moment the fault was logged. That snapshot is usually what separates a failing sensor from a real mechanical problem, and it is the first thing we look at before anything is unbolted.
Why the same code costs different money on a Mini
Each code on this page has a cost range rather than a price because the cheap cause and the expensive cause log identically. A split hose and a failed turbo can both set a boost code. Access matters too — some Mini engines put the awkward part behind half the front end, and the labour, not the part, is what moves the bill. An honest quote names which cause has been confirmed and what the repair for that specific cause costs.
Getting a Mini fault diagnosed
Bob's Mechanical Repairs is an independent, family-run garage in Birnam, Dunkeld, Perthshire, a couple of minutes off the A9. Bob has 32 years on the tools, and diagnostics are charged as diagnostic time with the findings explained in plain English and the repair priced before any work is agreed. An MOT is £54.85 if the car is due one at the same time.
Common questions
How do I read fault codes on a Mini? Any generic OBD-II reader will pull engine codes from a Mini built after 2001, but manufacturer-level codes from the gearbox, ABS and body modules need a tool that speaks the Mini protocols. That is why a garage scan often finds codes a cheap reader misses.
Will clearing a Mini fault code fix it? No. Clearing the code only erases the record. If the fault is still present it returns on the next drive cycle, and in the meantime the readiness monitors are reset, which can stop the car passing an emissions check.
How much is a Mini diagnostic at an independent garage? An hour of diagnostic time is typically £50–£90 in the UK, against £110–£180 at a main dealer. It almost always costs less than the part it stops you buying by mistake.